Can immunohistological analysis of transbronchial biopsy specimens predict responder status in early acute rejection of lung allografts?

The bronchus-associated-lymphoid tissue (BALT) an unique lymphoid organ in man and animals

The development structure and number of bronchus-associated lymphoid tissue (BALT) will be described in many different animals (like chicken, rabbit, mouse, rat, farm animals and particular the pig, monkey) and these data compared to healthy man and in human diseases. The term induced BALT should not be used because it is a tertiary lymphoid structure, which lacks the contact to a bronchus and does not consist of the important area (dome area) which is essential for antigen uptake of microbial stimuli, which are essential in the development of BALT. Mycoplasma seems to play a critical role as shown in pigs but there not been documented in other species like rabbits. More studies have to be performed in health and disease (e.g. in apes) to document the structural and functional basis to use BALT as an entry site for vaccination protocols.

Pathology of Lung Rejection: Cellular and Humoral Mediated

Acute rejection is an important risk factor for bronchiolitis obliterans syndrome, the clinical manifestation of chronic airway rejection in lung allograft recipients. Patients with acute rejection might be asymptomatic or present with symptoms that are not specific and can be also seen in other conditions. Clinical tests such as pulmonary function tests and imaging studies among others usually are abnormal; however, their results are also not specific for acute rejection. Histopathologic features of acute rejection in adequate samples of transbronchial lung biopsy of the lung allograft are currently the gold standard to assess for acute rejection in lung transplant recipients. Acute alloreactive injury can affect both the vasculature and the airways. Currently, the guidelines of the 2007 International Society of Heart and Lung Transplantation consensus conference are recommended for the histopathologic assessment of rejection. There are no specific morphologic features recognized to diagnose antibody-mediated rejection (AMR) in lung allografts. Therefore, the diagnosis of AMR currently requires a “triple test” including clinical features, serologic evidence of donor-specific antibodies, and pathologic findings supportive of AMR. Complement 4d deposition is used to support a diagnosis of AMR in many solid organ transplants; however, its significance for the diagnosis of AMR in lung allografts is not entirely clear. This chapter discusses the currently recommended guidelines for the assessment of cellular rejection of lung allografts and summarizes our knowledge about morphologic features and immunophenotypic tests that might help in the diagnosis of AMR.

Acute rejection

Despite induction immunosuppression and the use of aggressive maintenance immunosuppressive regimens, acute allograft rejection following lung transplantation is still a problem with important diagnostic and therapeutic challenges. As well as causing early graft loss and mortality, acute rejection also initiates the chronic alloimmune responses and airway-centred inflammation that predispose to bronchiolitis obliterans syndrome (BOS), also known as chronic lung allograft dysfunction (CLAD), which is a major source of morbidity and mortality after lung transplantation. Cellular responses to human leukocyte antigens (HLAs) on the allograft have traditionally been considered the main mechanism of acute rejection, but the influence of humoral immunity is increasingly recognised. As with other several other solid organ transplants, antibody-mediated rejection (AMR) is now a well-accepted and distinct clinical entity in lung transplantation. While acute cellular rejection (ACR) has defined histopathological criteria, transbronchial biopsy is less useful in AMR and its diagnosis is complicated by challenges in the measurement of antibodies directed against donor HLA, and a determination of their significance. Increasing awareness of the importance of non-HLA antigens further clouds this issue. Here, we review the pathophysiology, diagnosis, clinical presentation and treatment of ACR and AMR in lung transplantation, and discuss future potential biomarkers of both processes that may forward our understanding of these conditions.

Diagnosis of Acute Cellular Rejection and Antibody-Mediated Rejection on Lung Transplant Biopsies: A Perspective From Members of the Pulmonary Pathology Society

Context.—

The diagnosis and grading of acute cellular and antibody-mediated rejection (AMR) in lung allograft biopsies is important because rejection can lead to acute graft dysfunction and/or failure and may contribute to chronic graft failure. While acute cellular rejection is well defined histologically, no reproducible specific features of AMR are currently identified. Therefore, a combination of clinical features, serology, histopathology, and immunologic findings is suggested for the diagnosis of AMR.

Objective.—

To describe the perspective of members of the Pulmonary Pathology Society (PPS) on the workup of lung allograft transbronchial biopsy and the diagnosis of acute cellular rejection and AMR in lung transplant.

Data Sources.—

Reports by the International Society for Heart and Lung Transplantation (ISHLT), experience of members of PPS who routinely review lung allograft biopsies, and search of literature database (PubMed).

Conclusions.—

Acute cellular rejection should be assessed and graded according to the 2007 working formulation of the ISHLT. As currently no specific features are known for AMR in lung allografts, the triple test (clinical allograft dysfunction, donor-specific antibodies, pathologic findings) should be used for its diagnosis. C4d staining might be performed when morphologic, clinical, and/or serologic features suggestive of AMR are identified.

T cell immunohistochemistry refines lung transplant acute rejection diagnosis and grading

Objective

Lung transplant volume has been increasing. However, inaccurate and uncertain diagnosis for lung transplant rejection hurdles long-term outcome due to, in part, interobserver variability in rejection grading. Therefore, a more reliable method to facilitate diagnosing and grading rejection is warranted.

Method

Rat lung grafts were harvested on day 3, 7, 14 and 28 post transplant for histological and immunohistochemical assessment. No immunosuppressive treatment was administered. We explored the value of interstitial T lymphocytes quantification by immunohistochemistry and compared the role of T cell immunohistochemistry with H&E staining in diagnosing and grading lung transplant rejection.

Results

Typical acute rejection from grade A1 to A4 was found. Rejection severity was heterogeneously distributed in one-third transplanted lungs (14/40): lesions in apex and center were more augmented than in the base and periphery of the grafts, respectively. Immunohistochemistry showed profound difference in T lymphocyte infiltration among grade A1 to A4 rejections. The coincidence rate of H&E and immunohistochemistry was 77.5%. The amount of interstitial T lymphocyte infiltration increased gradually with the upgrading of rejection. The statistical analysis demonstrated that the difference in the amount of interstitial T lymphocytes between grade A2 and A3 was not obvious. However, T lymphocytes in lung tissue of grade A4 were significantly more abundant than in other grades.

Conclusions

Rejection severity was heterogeneously distributed within lung grafts. Immunohistochemistry improves the sensitivity and specificity of rejection diagnosis, and interstitial T lymphocyte quantitation has potential value in diagnosing and monitoring lung allograft rejection.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1536075282108217.

Bronchiolitis obliterans syndrome: the Achilles' heel of lung transplantation

Lung transplantation is a therapeutic option for patients with end-stage pulmonary disorders. Unfortunately, chronic lung allograft dysfunction (CLAD), most commonly manifest as bronchiolitis obliterans syndrome (BOS), continues to be highly prevalent and is the major limitation to long-term survival. The pathogenesis of BOS is complex and involves alloimmune and nonalloimmune pathways. Clinically, BOS manifests as airway obstruction and dyspnea that are classically progressive and ultimately fatal; however, the course is highly variable, and distinguishable phenotypes may exist. There are few controlled studies assessing treatment efficacy, but only a minority of patients respond to current treatment modalities. Ultimately, preventive strategies may prove more effective at prolonging survival after lung transplantation, but their remains considerable debate and little data regarding the best strategies to prevent BOS. A better understanding of the risk factors and their relationship to the pathological mechanisms of chronic lung allograft rejection should lead to better pharmacological targets to prevent or treat this syndrome.

Low CD4/CD8 Ratio in Bronchus-Associated Lymphoid Tissue Is Associated with Lung Allograft Rejection

Background. Bronchus-associated lymphoid tissue (BALT) has been associated with lung allograft rejection in rat transplant models. In human transplant recipients, BALT has not been linked to clinically significant rejection. We hypothesize that the immunohistochemical composition of BALT varies with the presence of acute lung allograft rejection. Methods. We retrospectively examined 40 human lung allograft recipients transplanted from 3/1/1999 to 6/1/2008. Patients were grouped by frequency and severity of acute rejection based on International Society of Heart Lung Transplant (ISHLT) criteria. Transbronchial biopsies were reviewed for BALT by a blinded pathologist. BALT if present was immunohistochemically stained to determine T-and B-cell subpopulations. Results. BALT presence was associated with an increased frequency of acute rejection episodes in the first year after transplantation. Patients with a lower CD4/CD8 ratio had an increased rejection rate; however, BALT size or densities of T-cell and B-cell subpopulations did not correlate with rejection rate. Conclusion. The presence of BALT is associated with an increased frequency of rejection one year after transplant. The lower the CD4/CD8 ratio, the more acute rejection episodes occur in the first year after transplantation. The immunohistochemical composition of BALT may predict patients prone to frequent episodes of acute cellular rejection.

Asthmatic granulomatosis: a novel disease with asthmatic and granulomatous features

RATIONALE

Severe asthma represents 5-10% of all asthma, yet remains problematic and poorly understood. Although it is increasingly recognized as consisting of numerous heterogenous phenotypes, their immunopathology, particularly in the distal airways and interstitium, remains poorly described.

OBJECTIVES

To identify the pathobiology of atypical difficult asthma.

METHODS

We report 10 from a total of 19 patients (17 women and 2 men) meeting asthma and severe asthma definitions, requiring daily systemic corticosteroid (CS) use, with inconsistent abnormalities on chest computed tomography scans, who underwent video-assisted thoracoscopic biopsies for further diagnosis and management.

MEASUREMENTS AND MAIN RESULTS

The pathology of 10 of the 19 cases revealed small airway changes consistent with asthma (eosinophilia, goblet cell hyperplasia), but with the unexpected finding of interstitial nonnecrotizing granulomas. These patients had no evidence for hypersensitivity pneumonitis, but 70% of cases had a personal or family history of autoimmune-like disease. The 10 cases were treated with azathioprine, mycophenolic acid, methotrexate, or infliximab. Nine of 10 showed decreased CS requirements and improved or maintained FEV(1) despite lower CS doses. Of the remaining nine patients, six manifested asthmatic small airway disease, alone or in combination with alveolar septal mononuclear cells, but no granulomas, whereas three manifested other pathologic findings (aspiration, pneumonia, or thromboemboli).

CONCLUSIONS

These data suggest that a subset of severe "asthma" manifests a granulomatous pathology, which we term "asthmatic granulomatosis." Although identification of this disease currently requires a thorascopic biopsy, alternative approaches to therapy lead to improvement in outcomes.

Pulmonary complications of lung transplantation

Lung transplantation is an effective treatment option for select patients with a variety of end-stage lung diseases. Although transplant can significantly improve the quality of life and prolong survival, a myriad of pulmonary complications may result in significant morbidity and limit long-term survival. The recognition and early treatment of these complications is important for optimizing outcomes. This article provides an overview and update of the pulmonary complications that may be commonly encountered by pulmonologists caring for these patients.

Lymph angiogenesis after lung transplantation and relation to acute organ rejection in humans

BACKGROUND

Acute rejection after kidney transplantation was found to be associated with increased recipient-derived lymph angiogenesis. However, the relation of lymph angiogenesis to acute rejection in lung transplantation has not yet been investigated.

METHODS

Transbronchial biopsies from 23 lung transplant recipients (47 + or - 15 years old, 15 male, 19 double lungs, 4 single lungs), taken at 14 and 90 days after transplantation were investigated. Immunohistostaining for PROX-1 (an lymphatic endothelial marker) and for vascular endothelial growth factor receptor (VEGFR) 1 and 2 (blood capillary markers) was performed. Biopsies with no sign of rejection (International Society for Heart and Lung Transplantation [ISHLT] grade A0, n = 27) were compared with biopsies with rejection grade A1/A2 (n = 19).

RESULTS

Biopsies with ISHLT rejection grade A1 or A2 showed a significantly higher density of PROX-1 marked lymphatics in comparison with biopsies of grade A0 at 14 days (p < 0.001) and at 90 days (p < 0.001) after transplantation, and in the collective comparison (all biopsies with ISHLT grade A1 or A2 versus all biopsies with grade A0, p < 0.001). For VEGFR-1 and VEGFR-2, no difference was found between ISHLT grade A1 or A2 compared with grade A0, neither at 14 or 90 days nor in the collective comparison.

CONCLUSIONS

Increased lymphatic angiogenesis after lung transplantation, demonstrated by increased density of the PROX-1 lymphatic endothelial marker, was associated with histologically evident acute organ rejection in humans. Although the exact role of lymphatic angiogenesis in acute organ rejection remains to be determined, further study of the interaction between the microvasculature and acute rejection seems warranted. Pending further investigation, analysis of PROX-1 density may develop into a new tool for rejection monitoring, supplementing conventional rejection grading.

Acute rejection and humoral sensitization in lung transplant recipients

Despite the recent introduction of many improved immunosuppressive agents for use in transplantation, acute rejection affects up to 55% of lung transplant recipients within the first year after transplant. Acute lung allograft rejection is defined as perivascular or peribronchiolar mononuclear inflammation. Although histopathologic signs of rejection often resolve with treatment, the frequency and severity of acute rejections represent the most important risk factor for the subsequent development of bronchiolitis obliterans syndrome (BOS), a condition of progressive airflow obstruction that limits survival to only 50% at 5 years after lung transplantation. Recent evidence demonstrates that peribronchiolar mononuclear inflammation (also known as lymphocytic bronchiolitis) or even a single episode of minimal perivascular inflammation significantly increase the risk for BOS. We comprehensively review the clinical presentation, diagnosis, histopathologic features, and mechanisms of acute cellular lung rejection. In addition, we consider emerging evidence that humoral rejection occurs in lung transplantation, characterized by local complement activation or the presence of antibody to donor human leukocyte antigens (HLA). We discuss in detail methods for HLA antibody detection as well as the clinical relevance, the mechanisms, and the pathologic hallmarks of humoral injury. Treatment options for cellular rejection include high-dose methylprednisolone, antithymocyte globulin, or alemtuzumab. Treatment options for humoral rejection include intravenous immunoglobulin, plasmapheresis, or rituximab. A greater mechanistic understanding of cellular and humoral forms of rejection and their role in the pathogenesis of BOS is critical in developing therapies that extend long-term survival after lung transplantation.

Quantitation of T lymphocytes in posttransplant transbronchial biopsies

The diagnostic role of immunohistochemical staining for T lymphocytes in grading acute airway rejection has not been fully explored. We examined 136 transbronchial biopsies from 52 lung transplant patients and 9 nontransplant controls. Transplant rejection was based on histologic assessment of perivascular (A) and bronchiolar (B) infiltrates. The clinical indication for the 136 allograft biopsies was routine surveillance (n = 72), decreased pulmonary function, rule out rejection (n = 36), suspect infection (n = 16), rule out obliterative bronchiolitis (n = 6), and persistent postoperative graft failure (n = 6). T lymphocytes were counted in bronchial mucosa per 100 bronchial epithelial cells, and in alveolar walls per square millimeters, after immunohistochemical staining with anti-CD3, CD4, and CD8. In controls, the mean alveolar wall CD3 cell count was 45 per square millimeter (95% confidence intervals, 30-52 per square millimeter) and the mean CD8 count was 15 per square millimeter (2-20 per square millimeter). In surveillance and negative patient biopsies, alveolar wall CD8 counts were significantly greater than controls (P = .03 and .02, respectively). Mean alveolar wall CD3 counts were significantly higher in type A rejection (88.7 +/- 12.9) than controls and negative biopsies (42 +/- 5.3, P < .001), but there was no difference compared to infections (119.7 +/- 22, P > .5). Mucosal CD3 cell counts were significantly higher in type B rejection (16.1 +/- 2.5) than controls and negative biopsies (1.5 +/- 0.4, P < .001), and also higher than infections (3.9 +/- 1.1, P < .001). In 7% of biopsies, T-cell staining identified perivascular circumferential infiltrates that were difficult to identify on routine stains, and in an additional 9% minor changes in grading were made after reviewing T-cell markers. Immunohistochemical staining may help in identifying perivascular infiltrates and demonstrates increased intraepithelial T-cells even in low-grade type B rejection. Type B rejection as assessed quantitatively is more specific than type A rejection in comparison to infection.

Lung

Experiments with animals in the 1940 and 1950s demonstrated that lung transplantation was technically possible [33]. In 1963, Dr. James Hardy performed the first human lung transplantation. The recipient survived 18 days, ultimately succumbing to renal failure and malnutrition [58]. From 1963 through 1978, multiple attempts at lung transplantation failed because of rejection and complications at the bronchial anastomosis. In the 1980s, improvements in immunosuppression, especially the introduction of cyclosporin A, and enhanced surgical techniques led to renewed interest in organ transplantation. In 1981, a 45-year-old-woman received the first successful heart–lung transplantation for idiopathic pulmonary arterial hypertension (IPAH) [106]. She survived 5 years after the procedure. Two years later the first successful single lung transplantation for idiopathic pulmonary fibrosis (IPF) [128] was reported, and in 1986 the first double lung transplantation for emphysema [25] was performed.

Severity of lymphocytic bronchiolitis predicts long-term outcome after lung transplantation

RATIONALE

Severe and recurrent acute vascular rejection of the pulmonary allograft is an accepted major risk factor for obliterative bronchiolitis.

OBJECTIVES

We assessed the role of lymphocytic bronchiolitis as a risk factor for bronchiolitis obliterans syndrome (BOS) and death after lung transplantation.

METHODS

Retrospective analysis of 341 90-day survivors of lung transplant performed in 1995-2005 who underwent 1,770 transbronchial lung biopsy procedures.

MEASUREMENTS AND MAIN RESULTS

Transbronchial biopsies showed grade B0 (normal) (n = 501), B1 (minimal) (n = 762), B2 (mild) (n = 176), B3 (moderate) (n = 70), B4 (severe) (n = 4) lymphocytic bronchiolitis, and Bx (no bronchiolar tissue) (n = 75). A total of 182 transbronchial biopsies were ungraded (8 inadequate, 142 cytomegalovirus, 32 other diagnoses). Lung transplant recipients were grouped by highest B grade before diagnosis of BOS: B0 (n = 12), B1 (n = 166), B2 (n = 89), and B3-B4 (n = 51). Twenty-three were unclassifiable. Cumulative incidence of BOS and death were dependent on highest B grade (Kaplan-Meier, P < 0.001, log-rank). Multivariable Cox proportional hazards analysis showed significant risks for BOS were highest B grade (relative risk [RR], 1.62; 95% confidence interval [CI], 1.31-2.00) (P < 0.001), longer ischemic time (RR, 1.00; CI, 1.00-1.00) (P < 0.05), and recent year of transplant (RR, 0.93; CI, 0.87-1.00) (P < 0.05), whereas risks for death were BOS as a time-dependent covariable (RR, 19.10; CI, 11.07-32.96) (P < 0.001) and highest B grade (RR, 1.36; CI, 1.07-1.72) (P < 0.05). Acute vascular rejection was not a significant risk factor in either model.

CONCLUSIONS

Severity of lymphocytic bronchiolitis is associated with increased risk of BOS and death after lung transplantation independent of acute vascular rejection.

Human Leukocyte Antigen Antibodies for Monitoring Transplant Patients

Human leukocyte antigen (HLA) antibody-mediated hyperacute rejection has dramatically decreased since the clinical introduction of crossmatch technology. However, the role of HLA antibody in acute and chronic rejection remains unclear. In this article, we cite publications to show the correlation between HLA antibody and allograft rejection. Potential pathological mechanisms of antibody-mediated rejection are also proposed and the rationale of commonly used HLA antibody detection techniques are introduced. The advantages and disadvantages of these technologies are further discussed in detail. We conclude that owing to the recent availability of improved antibody detection methods, a causal relationship between HLA antibodies and allograft rejection is now considered to exist.

HLA-specific antibodies are risk factors for lymphocytic bronchiolitis and chronic lung allograft dysfunction

Bronchiolitis obliterans syndrome (BOS) represents a major limitation in lung transplantation. While acute rejection is widely considered the most important risk factor for BOS, the impact of HLA-specific antibodies is less understood. Of 51 lung recipients who were prospectively tested during a 4.2 +/- 1.6-year period, 14 patients developed HLA-specific antibodies. A multi-factorial analysis was performed to correlate the prevalence of BOS with HLA antibodies, persistent-recurrent acute rejection (ACR-PR), lymphocytic bronchiolitis, and HLA-A, -B, and -DR mismatches. HLA-specific antibodies were associated with ACR-PR (10/14 vs. 11/37 with no antibodies, p < 0.05), lymphocytic bronchiolitis (8/14 vs. 10/37, p < 0.05), and BOS (10/14, vs. 9/37, p < 0.005). Other risk factors for BOS were: lymphocytic bronchiolitis (13/18 vs. 6/33 with no lymphocytic bronchiolitis, p < 0.0001), ACR-PR (12/21 vs. 7/30 with no ACR-PR, p < 0.05), and the number of HLA-DR mismatches (1.7 +/- 0.48 in BOS vs. 1.2 +/- 0.63 without BOS, p < 0.05). The presence of antibodies exhibited a cumulative effect on BOS when it was associated with either lymphocytic bronchiolitis or ACR-PR. The complex relationship between the development of HLA antibodies and acute and chronic lung allograft rejection determines the importance of post-transplant screening for HLA-specific antibodies as a prognostic element for lung allograft outcome.

National conference to assess antibody-mediated rejection in solid organ transplantation

The process of humoral rejection is multifaceted and has different manifestations in the various types of organ transplants. Because this process is emerging as a leading cause of graft loss, a conference was held in April 2003 to comprehensively address issues regarding humoral rejection. Though humoral rejection may result from different factors, discussion focused on a paradigm caused by antibodies, typically against donor HLA antigens, leading to the term 'antibody-mediated rejection' (AMR). Conference deliberations were separated into four workgroups: The Profiling Workgroup evaluated strengths and limitations of different methods for detecting HLA reactive antibody, and created risk assessment guidelines for AMR; The Diagnosis Workgroup reviewed clinical, pathologic, and serologic criteria for assessing AMR in renal, heart and lung transplant recipients; The Treatment Workgroup discussed advantages, limitations and possible mechanisms of action for desensitization protocols that may reverse AMR; and The Basic Science Workgroup presented animal and human immunologic models for humoral rejection and proposed potential targets for future intervention. This work represents a comprehensive review with contributions from experts in the fields of Transplantation Surgery, Medicine, Pathology, Histocompatibility, Immunology, and clinical trial design. Immunologic barriers once considered insurmountable are now consistently overcome to enable more patients to undergo organ transplantation.

Soluble donor HLA class I and beta 2m-free heavy chain in serum of lung transplant recipients: steady-state levels and increases in patients with recurrent CMV infection, acute rejection episodes, and poor outcome

We determined the concentration of donor sHLA/beta(2)m and total beta(2)m-free heavy chain (HC) in the serum of lung transplant recipients with ELISA assays. While we were unable to detect specific donor beta(2)m-free HCs due to a lack of available antibodies, we could determine if events that led to an increase in the release of beta(2)m-free HC also led to an increase in the release of donor sHLA/beta(2)m, particularly the 36 kDa, proteolytically cleaved form. We found that lung transplants constituitively release donor sHLA/beta(2)m at ng/ml levels. The levels (both of donor sHLA/beta(2)m and total beta(2)m-free HC) were significantly increased in CMV-sero-negative recipients (but not in CMV-sero-positive recipients) at the onset of post-transplant CMV disease. Acute rejection episodes were also associated with an increased release of donor sHLA/beta(2)m, but not of beta(2)m-free HC. However, in patients with particularly poor outcome (i.e., graft loss within 1 year) there was a significant release of beta(2)m-free HC. Analysis of one such patient showed a predominance of 36 kDa forms of donor-sHLA/beta(2)m. Our data are consistent with the hypothesis that the metalloproteinase that cleaves beta(2)m-free HC is active during uncontrolled CMV infection and acute rejection. However, recall responses to CMV and controlled immune responses to donor may result in little or no activation of sHLA class I release.

The significance of bronchus-associated lymphoid tissue in human lung transplantation: is there an association with acute and chronic rejection?

BACKGROUND

In animal models of acute rejection in lung allografts, bronchus-associated lymphoid tissue (BALT) plays a major role in the induction and persistence of the alloreactive response. We undertook a study of the clinical and histologic associations with BALT identified on transbronchial biopsy in human lung allograft recipients.

METHODS

Transbronchial biopsies of patients receiving single lung, double lung, and combined heart-lung transplantation from 1984 to 1997 at the University of Pittsburgh Medical Center were reviewed. Seventy-seven patients had transbronchial biopsies demonstrating BALT. We examined all pathologic reports and slides, and graded rejection utilizing the Revised Working Formulation for the Classification of Pulmonary Allograft Rejection. Twenty-nine of 77 patients were selected at random to evaluate the distribution of BALT lymphocyte subsets immunohistochemically.

RESULTS

There was no relationship between native disease or the transplant procedure and the identification of BALT. BALT was found from 9 days to 2431 days after transplant (average: 440 days; median: 157 days) in association with clinically insignificant acute cellular rejection (A0, A1) in 75% of cases. Bronchiolitis obliterans developed in 29% of patients with a BALT-positive biopsy, a percentage not different from that of our overall lung transplant population. Immunohistochemical examination of BALT showed helper T cells predominated over cytotoxic T cells in zones surrounding B cell-rich follicular center cells.

CONCLUSIONS

The association of BALT with high-grade acute cellular rejection and with the development of bronchiolitis obliterans could not be confirmed in human lung allografts. BALT most often accompanied A0 or A1 rejection. This raises the possibility that the presence of BALT on transbronchial biopsy may be part of the evolution of immunologic tolerance in human pulmonary allografts.

MIB-1 as a predictor of response in lung allografts with moderate acute cellular rejection

The major obstacle that long-term lung transplant recipients face is bronchiolitis obliterans. Prior episodes of acute rejection, specifically their frequency, persistence, and severity, are important predictors of bronchiolitis obliterans. Many cells contribute to the damage of acute rejection, and there is no sole cell type that can predict persistent rejection or bronchiolitis obliterans. In this study we evaluated 48 transbronchial biopsy samples from various grades of acute rejection with the proliferation marker MIB-1 and attempted to retrospectively predict response to standard corticosteroid in a subpopulation of nine responders and nine nonresponders, all with grade A3 rejection. We then characterized the proliferating cells by double labeling with MIB-1 and L26, CD3, OPD4, or KP1. Our results indicate that the proliferating cells in acute lung rejection are a heterogeneous pool of T- and B-lymphocytes, T-helper cells, macrophages, endothelial cells, and possibly parenchymal cells, and that MIB-1 is a valuable tool in the evaluation of total cellular activity in this setting. In addition, the overall proliferation rate, defined as the most intense proliferation rate regardless of location in the biopsy, closely matches the grade of acute rejection. Finally, a low lesional proliferation rate, defined as the proliferation rate at the site of perivascular inflammation diagnostic of acute rejection, is an indicator of excellent response to therapy and may have potential clinical importance.

Decreased expression of the cystic fibrosis transmembrane conductance regulator protein in remodeled airway epithelium from lung transplanted patients

The absence or mislocalization of cystic fibrosis transmembrane conductance regulator (CFTR) is regarded as being specific for cystic fibrosis (CF). In principle, the supply of a non-CF lung transplant to a CF patient should bring up normal CFTR expression in the lower airways. Immunolocalization of CFTR and of epithelial differentiation markers (ie, cytokeratins 13, 14, and 18, and desmoplakins 1 and 2) was carried out on 21 mucosal biopsies from the upper lobe of grafts in non-CF (n = 12) and CF patients (n = 9) retrieved between days 23 and 1,608 after lung transplantation. Biopsy specimens from seven non-CF and four CF patients presented either a pseudostratified respiratory epithelium or slight basal cell hyperplasia. CFTR was distributed at the apical membrane of the ciliated cells. In remodeled epithelia with basal cell hyperplasia or squamous metaplasia, CFTR was either weakly expressed in the cytoplasm of the superficial epithelial cells or was undetectable. The extent of epithelium remodeling was significantly correlated with an impairment of lung function. The results suggest that posttransplant airway epithelium dedifferentiation of the graft leads to the loss of properly targeted CFTR irrespective of the underlying disease of the recipient.

Acute pulmonary allograft rejection. Mechanisms, diagnosis, and management

Rejection is a common complication following lung transplantation, and can lead to considerable short- and long-term morbidity. As numbers and survival rates of lung transplant recipients increase, it is apparent that acute rejection can occur months or years after transplantation, and may be resistant to standard therapies. Mechanisms of acute rejection have been well studied in other solid organ transplant recipients, and are beginning to be addressed in the lung recipient. This article addresses some of the common issues of diagnosis and management of acute rejection which arise frequently during the care of lung transplant recipients.

Medical management and complications in the lung transplant recipient

Lung transplantation has evolved as a viable therapy for patients with end-stage lung disease. Improvements in surgical techniques, avoidance of rejection by effective strategies of immunosuppression, and other aspects of medical management allow successful lung transplantation, with 1-year survivorship of 70 to 93%. In this review, we address the medical management of patients who have undergone lung transplantation. The immunosuppressive protocol used at Mayo Clinic Rochester is presented, along with a discussion of the mechanisms of action and potential complications associated with the various drugs used. The recognition and treatment of early graft dysfunction, infection, rejection, stenosis of the airway anastomosis, and posttransplantation lymphoproliferative disorder are also reviewed. Careful surveillance of patients after lung transplantation helps maintain graft function and facilitates identification, treatment, and potential avoidance of complications.

Significance of clinically silent untreated mild acute cellular rejection in lung allograft recipients

Although acute rejection is a frequent occurrence after transplantation, the clinical behavior and pathological manifestations of untreated mild acute cellular rejection in clinically stable lung allograft recipients is poorly defined. Sixteen patients were identified who had asymptomatic mild acute rejection that was untreated but followed by subsequent pulmonary function tests and repeat transbronchial biopsy. Six patients had spontaneous resolution of their infiltrates; the condition of 10 patients worsened as observed from their biopsies or function studies. Those who worsened had more episodes of acute rejection per patient before the A2 biopsy (2.0 vs 1.3), and 50% developed bronchiolitis obliterans compared with 16% in the spontaneously regressing group. Pathological evaluation showed that patients with persistent or worsening untreated A2 rejection tended to have more large and small airway inflammation, larger numbers of eosinophils and plasma cells in their biopsies, and airway and airspace granulation tissue. These variables may be used to help determine which low grade lung rejection episodes should receive adjunctive immunosuppressive therapy.